Synchronization in the unified chaotic systems with uncertain parameters is discussed in this paper. Based on the stability theory of a cascade-connected system, control laws are presented to achieve synchronization in the unified chaotic systems with uncertain parameters. The advantage of the proposed controllers is that they are linear, simple, robust and only part parameters are required to be bounded. Finally, Simulation results for the Lorenz, Lu and Chen chaotic systems are provided to illustrate the effectiveness of the proposed scheme.